By SCOTT SHANE

January 16, 2013

FORT MEADE, Md. — When he was hired in 2010 to defend Pfc. Bradley Manning, David E. Coombs was handed the most daunting of challenges.

Private Manning, it turned out, had admitted on Internet chat logs to taking thousands of confidential government documents from his computer in Iraq and delivering them to WikiLeaks, the antisecrecy organization. Furious military and State Department officials spoke of grave damage to national security and danger to people named in the documents. Members of Congress muttered about treason and the death penalty.

More than two and a half years later, Mr. Coombs, 43, is deep into one of the most high-profile American military cases in recent years, leading an aggressive, if unorthodox, defense. In weeks of pretrial hearings, the tall, crew-cut lawyer, flanked by uniformed military lawyers who make up the rest of the defense team, has attacked the government’s case on every conceivable ground, even as he conceded that Private Manning was the WikiLeaks source.

Mr. Coombs, a lieutenant colonel in the Army Reserve, served 12 years in the Army before leaving active duty and opening a military-oriented defense practice in 2009 in Providence, R.I. He has worked, both in court and in a public speech last month, to frame Private Manning’s disclosure of documents not as a reckless act of national security vandalism but as a deed of conscience, intended to expose government misdeeds and defend the public’s right to know.

But on Wednesday, the military judge in the case, Col. Denise Lind of the Army, ruled that the defense could not present evidence of Private Manning’s political motives at trial.

Mr. Coombs did win a modest victory when the judge ruled that Private Manning, who is charged with “aiding the enemy,” could try to show that he did not know that in passing government documents to WikiLeaks he was indirectly providing them via the Web to Al Qaeda. Some were found on Osama bin Laden’s computer.

She also ruled that Private Manning could argue that he was selective in choosing the 700,000 documents he is accused of releasing and that a reasonable person would not have reason to believe that the leaked material would harm the United States.

The ruling will prevent the defense from making a sweeping claim that Private Manning’s acts were in the public interest — an argument that Mr. Coombs hinted at in his only public remarks, to an enthusiastic crowd at a Washington church in early December.

“It’s a case that has significance for all of us,” Mr. Coombs said then. “We live in a country that is built on freedom of speech. We live in a country that is built on government accountability and informed citizens.”

In earlier proceedings, Mr. Coombs battled the military authorities over Private Manning’s treatment in a military jail at Quantico, Va., and turned the decision to strip him of clothing at night into a pretrial issue. The result was modest: the judge agreed that the treatment was improper but ordered only 112 days deducted from any future sentence.

A brainy intelligence analyst of slight build who felt misplaced in the military, Private Manning struggled with issues of gender and sexuality. But in the chat logs, he suggested that he was disclosing the documents because of concerns about the legality and ethics of the Iraq war and other American government actions. He has been embraced since his arrest as a whistle-blower and hero by many on the political left, including Daniel Ellsberg, who leaked the Pentagon Papers four decades ago.

“I think Coombs is doing an amazing job,” said Emma Cape, 26, one of four full-time employees of the Bradley Manning Support Network, which has raised the money to pay Mr. Coombs and campaign for his client.

In weeks of pretrial hearings, Ms. Cape said, she has come to admire Mr. Coombs’s dedication, recalling how court-watchers learned at the end of a 10-hour day last fall that it was Mr. Coombs’s wedding anniversary. A Manning supporter rushed out for roses and a card for the lawyer and his wife, Tanya J. Monestier, a law professor who sometimes attends court sessions.

In calling witness after witness to expose Private Manning’s mistreatment at Quantico, “Coombs created a compelling narrative,” Ms. Cape said. She called the lawyer “incredibly warm to the people who come to court day after day.”

But several veteran military defense lawyers said they were baffled by some elements of Mr. Coombs’s approach. In particular, they wonder why he has stated in court that Private Manning is prepared to plead guilty to a list of crimes that carry a total maximum sentence of 20 years. The list consists of lesser versions of the full charges, which could send the soldier to prison for life without parole.

“I’ve never seen it before,” said Eugene R. Fidell, who teaches military justice at Yale. “Plea negotiations are not conducted in public.”

Gary Myers, a military defense lawyer for 45 years, commended Mr. Coombs’s “creative thinking” but expressed similar puzzlement about the unilateral offer of a guilty plea.

Mr. Coombs did not respond to questions about his strategy. Most legal experts expect the case to be resolved with a guilty plea, but a trial is now scheduled for June 3.

In court on Wednesday, Mr. Coombs argued that the government had violated his client’s right to a speedy trial. Prosecutors argued that even during periods of “apparent inactivity,” they were working away on a very complex case, sending hundreds of e-mails and studying the law.

Outside, near the gate to Fort Meade, pro-Manning protesters displayed the time elapsed since Private Manning’s arrest: 964 days.